AmmoMaster® Chronograph Operating Instructions ... - RCBS

AmmoMaster ® Chronograph 

Operating Instructions 

All of us at RCBS ® would like to thank you for purchasing the 

AmmoMaster ® Chronograph. We believe, dollar for dollar, it is the best 

chronograph on the market. 

ThoRoughly ReAd All diReCTionS And SAfeTy inSTRuCTionS 

inCluded in ThiS pACkAge. 

If you have any questions or problems, do not return it to the 

store. Instead, call us at (800) 533-5000 or (530) 533-5191 and 

we will be happy to help you. 

FEATURES 

• 86 square inches of available shooting area. 

• Detachable Display Unit with 20 foot cord. 

• High, Low and Average data-string velocity readings. 

• Extreme Spread and Standard Deviation data-string calculations. 

• Edit data-string functions and delete data functions. 

• Feet/second (f/s) or meter/second (m/s) velocity readings. 

• Low battery indicator 

• Full string indication 

• 10 strings maximum stored in memory with 10 shot velocity 

measurements per string 

• Warranty of 1 year from date of purchase. 

SPECIFICATIONS 

Velocity Range: 70 – 7000 fps (21 – 2134 m/s) 

Clock speed: 10 MHz 

Power Requirements: 9 Volt DC battery 

Operating Temperature Range: 20 – 120º F 

SAFETY AND WARNINGS 

READ THOROUGHLY ALL DIRECTIONS AND SAFETY 

INSTRUCTIONS INCLUDED IN THIS PACKAGE. FAILURE TO COMPLY 

MAY RESULT IN AN UNSAFE FIREARM CONDITION THAT MAY CAUSE 

PROPERTY DAMAGE, PERSONAL INJURY OR DEATH. 

WARNING! 

• TARGET MUST HAVE A SAFE BACKSTOP. 

• BYSTANDERS MUST STAY BEHIND THE SHOOTERS AT ALL TIMES. 

• ALWAYS WEAR EYE AND HEARING PROTECTION. Shooter must 

maintain proper eye relief from optical sighting devices and wear 

eye protection at all times. 

• FOLLOW LOCAL, STATE AND FEDERAL LAWS REGARDING 

FIREARM USE. 

ALWAYS FOLLOW THE RULES OF FIREARM SAFETY. 

UNLOAD FIREARM, OPEN FIREARM ACTION AND ENGAGE FIREARM 

SAFETY BEFORE MAKING ANY FIREARM ADJUSTMENTS. DO NOT 

REACH IN FRONT OF FIREARM MUZZLE TO MAKE ADJUSTMENTS. 

ALWAYS KEEP FIREARM MUZZLE POINTED IN A SAFE DIRECTION 

WHEN MAKING ADJUSTMENTS, LOADING FIREARM AND 

DISCHARGING FIREARM. CARE SHOULD BE TAKEN TO ENSURE 

THAT THERE IS NOT INTERFERENCE WITH THE FIREARM STOCK, 

SLING OR ACTION. 

WARNING! Never exceed published recommended gun 

powder amounts in reloads to achieve higher velocities in your 

ammunition. Increasing the amount of powder could cause a 

dangerous condition that may cause property damage, personal 

injury or death. 

WARNING! Velocity measurements should not be used to 

calculate combustion pressures in your cartridge or chamber. Again, do 

not exceed published maximum powder levels in your ammunition. 

WARNING! do noT try to protect your chronograph with armor 

plating. Bullet ricochet from hitting this plating could cause property 

damage, personal injury or death. Chronograph components are 

replaceable. 

All chronograph units have inherent uncertainty when recording 

velocity measurements. Several uncontrollable variables can affect 

each measurement and contribute to this uncertainty, including sunlight 

intensity, sunlight orientation, cloud cover, wind, shadows, and ground 

reflectivity of cement, water, or snow, etc. When collecting data, be 

suspicious of any data points that have greater than a 4% difference of 

that ammo’s average string velocity. 

Special care should be taken when shooting certain types of 

ammunition. gas checks, wads, sabots, etc. can separate and impact 

your chronograph causing damage to the device. 

Also, as with any electronic device, water can damage certain 

components. Be careful when using the chronograph outdoors in rainy 

weather to prevent damage to the Keypad/Display Unit or Skyscreens. 

ITEM NO. PART NUMBER DESCRIPTION QTY. 

1 Body 1 

2 Keypad/Display Unit 1 

3 Keypad/Display Unit Cover 1 

4 Body lid 1 

5 81191 Side Support (set of 2) 2 

6 81192 Diffuser (3 part assembly) 2 

7 81193 Skyscreens 2 

Figure 1 - RCBS ® AmmoMaster ® Chronograph 

RCBS AmmoMaster ® Chronograph Instructions 1

UNPACKING 

1. Detach the Keypad/Display Unit from the chronograph’s body by 

depressing the locking tab on top of the unit and pulling straight off. 

Try not to twist or bend display unit while performing this action. 

The display will be kept near the shooter during use. 

2. The AmmoMaster ® Chronograph has an internal storage 

compartment. The base or ‘headstamp’ end of the chronograph has 

a removable door. Depress the tab to remove the door (See Figure 2). 

Figure 2 - Storage Compartment 

3. Remove the peripheral equipment from inside the chronograph’s 

body. There should be 2 Skyscreens (Item 7), 2 Diffuser Assemblies 

(Item 6), and 4 Side Supports (Item 5) shown in Figure 1. 

ASSEMBLY 

1. Attach the chronograph base unit to any camera tripod (not included) 

that uses a standard 1/4"-20 mounting screw or place the unit on a 

stable and level surface like a table or workbench (See Figure 3). 

Figure 3 

2 RCBS AmmoMaster ® Chronograph Instructions 

Figure 4 

2. Unwrap the Skyscreen cable and locate the label at the end of the 

cable, which will be labeled “Start” for the Start Skyscreen, or “Stop” 

for the Stop Skyscreen. plug the end of the cable, from each of the 

two Skyscreens, into the backside of the Display Unit (See Figure 4). 

Make sure the Skyscreens are plugged into the correct socket, i.e., 

Start Skyscreen should be plugged into the RgA Jack marked “Start” 

and the Stop Skyscreen plugged into the RgA Jack marked “Stop”. The 

chronograph will not record velocities accurately if the Start and Stop 

Skyscreens are plugged into an incorrect jack. (See Figure 4). 

3. Place the Start Skyscreen in the first slot located in the front of the 

chronograph’s body/case. Place the Stop Skyscreen in the slot located 

at the rear of the case (See Figure 3 and 5). The Skyscreens are 

secured in place by a spring clip. once installed, give the skyscreens 

a slight pull to ensure they are securely locked into place. Velocity 

readings may be inaccurate if the Skyscreens are not fully inserted 

into their respective mounting slots. 

Figure 5 

4. Once the Skyscreens are installed, place one Side Support Arm onto 

the side of each Skyscreen by aligning the ball into the keyholeshaped 

slot and then press the support arm down to lock the arm 

into position (See Figure 6).

Figure 6 

5. The next step is to assemble the Diffusers. Each Diffuser consists of 

one middle piece and two end pieces. The notches on the diffuser are 

numbered with either a number “1” or “2” to help aid in assembly. 

Take the middle piece and one of the end pieces, line up the matching 

numbers and simply slip into position (See Figure 7). 

Figure 7 

6. Insert the Diffuser’s tab into the Support Arm’s slot so the ribs on the 

diffuser are facing down toward the Skyscreen as shown in figure 

8. While holding the Diffuser horizontal, install the other Support Arm 

onto the opposite side of this diffuser and then connect this Support 

Arm to the Skyscreen the same way you did in Step #4. 

Figure 8 

7. Repeat steps 4 – 6 for the other Skyscreen location. 

SET-UP 

ALWAYS WEAR EYE AND HEARING PROTECTION. 

1. Place the assembled chronograph unit on a stable surface or tripod 

(not included). Ensure the Chronograph is level and oriented in the 

same direction as the bullet/projectile’s path, otherwise it could give 

you erroneous velocity readings. 

2. The Front Skyscreen, for typical rifle calibers (.308 or smaller), should 

be at least 10 feet away from the muzzle of the weapon (See Figure 

9). Larger calibers, magnums, etc., produce more muzzle blast that 

can falsely trigger the Skyscreen and produce erroneous velocity 

readings. Increase the distance to 16' - 18' to eliminate this issue. 

10' 

Figure 9 

3. Bring the Display Unit back to your firing position. Turn the Display 

Unit on by pressing the On/Off button. You will see the following 

display for a moment while the unit initializes (See Figure 10). 

4" 


Figure 10 - Initialization Screen 

4. Once the Display shows a shot number and an indicator next to 

“Ready”, the AmmoMaster ® unit is ready to record velocities (See 

Figure 11). 

Figure 11 - “Ready” on Shot #1 

5. Measure the distance between the bore of the weapon system and 

the sighting system. Typically this distance is 1.5" on a rifle with an 

optical scope. Remember that your line of sight will be higher than 

the path of the projectile. The ideal projectile path is centered over the 

chronograph at a height of 4.0 inches above the top of the Skyscreen 

(See Figure 9). The projectile/ bullet height should be kept within ± 

1.5 inches of this location for accurate velocity measurements. 

WARNING! BE CAREFUL NOT TO AIM ANY LOWER THAN 

THIS, AS IT MAY CAUSE SERIOUS DAMAGE TO THE 

SKYSCREEN AND POTENTIALLY CAUSE SERIOUS INJURY TO 

THE SHOOTER. 

a. We recommend using a bench, sand bags, bi-pods, or other 

means to stabilize your weapon. 

b. if you are concerned about hitting your chronograph, start by 

removing your diffusers and Side Supports. place a paper target 

immediately behind your chronograph and aim several inches 

above the top surface of the Skyscreens. Work your shots lower 

in small increments until your shot placement is in the correct 

location. Make note of that aiming spot. if desired, place a piece of 

tape on the Side Support as a visual reference for your aim point 

of that particular firearm. Repeat this procedure for each weapon 

used in conjunction with your chronograph. 

6. Shoot a round at the correct aiming point as mentioned above, to 

start recording your velocity measurements. 

ALWAYS WEAR EYE AND HEARING PROTECTION. 

7. Please refer to the detailed instructions listed on pages 5-8 

to become more familiar with the full functionality of the 

AmmoMaster ® Chronograph. 

8. ENJOY. 


STORAGE 

Follow steps 1 – 7 of the “Assembly” section in reverse sequence. Your 

Chronograph should be stored in a dry, cool place away from direct 

sunlight if possible. Although the plastic components of your unit are 

manufactured with a uV inhibitor additive, limiting unnecessary uV 

exposure of any plastic device is recommended. Do not leave your unit 

outside for long periods of time. 

KEYPAD LAYOUT 

BUTTON FUNCTION DESCRIPTION 

power Button Turn unit On. Turn unit Off, depress button and hold for 3-5 sec. 

Change units Depress to switch from f/s to m/s. 

Scroll left 

Scroll Right 

Adds data 

to string 

Scroll to the left (decreasing shot #) while in Stats Mode and 

edit String Mode 

Scroll to the right (increasing shot #) while in Stats Mode and 

edit String Mode 

Add data to an existing shot string while in Edit String Mode 

no command depress no if choose not to delete velocity or string or clear all. 

enter edit 

String Mode 

delete data 

in string 

edit String Mode allows editing of recorded velocities in 

selected shot strings. 

delete current velocity recorded; delete any recorded velocity 

in any shot string. 

yes command depress yes if choose to delete velocity or string or clear all. 

enter Stats 

Mode 

Clear a 

selected string 

delete all 

recorded data 

Accept results 

Starts new 

shot string 

displays statistical data for a selected shot string. 

Clear function will clear all data within a selected shot string. 

Reset will clear all recorded data in all shot strings. 

depress enter to select desired shot string, accepts the results 

in the stats mode. 

Starts new shot string 

FUNCTIONS 

On/Off 

To turn unit on - depress “On/Off” button and the Chronograph is 

ready to record data. 

To turn unit off - depress “On/Off” button and hold for approximately 

3-5 seconds.

m/s – f/s 

Switches units from feet per second or meters per second. 

To switch between units simply depress the m/s – f/s button. 

Enter 

depressing the “enter” button accepts the current string and starts 

a new string, accepts string while in edit string mode and accepts 

the results in the stats mode and readies unit for recording of the 

next velocity. 

Scroll ( ) 

Allows user to scroll to the right or the left while in Stats Mode 

to view statistical information, and for scrolling through recorded 

strings or recorded shot velocities (1, 2, 3,… , 10). 

Delete Data 

delete current velocity recorded; delete any recorded velocity in 

any of the recorded strings, while in edit string mode. 

Add Data 

depressing “Add data” button while in edit String Mode will 

prepare unit to record shot velocity within existing shot string, 

if string is not currently full. data will be appended to the end of 

the string. 

Yes or No 

Depressing the “Yes” or “No” button will confirm/deny the deletion of 

a recorded velocity, entire shot string, or all recorded shot velocities. 

Edit String 

Allows user to enter the “edit String” mode and edit the recorded 

velocities in a desired shot string. 

Clear/Reset 

This allows the user to delete a shot string or all recorded data 

stored in the unit. 

Start New String 

A new string may be started at any time. depressing the “enter” 

button will accept current string and start a new string. 

Delete Velocity 

To delete current recorded velocity, simply depress “delete 

data” button, “del” will display with an indicator above “Shot”. 

Depress “Yes” button to confirm deletion of the last velocity 

recorded or the “no” button to deny deletion and ready unit to 

record next shot velocity. 

For recorded velocity in different string, simply depress “edit 

String” button. use “Scroll” buttons to scroll through desired shot 

strings; press “enter” to select desired string, use “Scroll” buttons 

to scroll through recorded shot velocities. if choose to delete 

recorded velocity depress “delete” button, “del” will be displayed 

with an indicator above “Shot”. Press “Yes” button to confirm 

deletion, if choose not to delete velocity press “No” button. To exit 

edit string mode and ready unit for next shot within existing shot 

string that is not full, depress the “Add data” button or “enter” 

button. for a full string, depress the “enter” button twice to begin 

a new shot string. 

Delete String 

Depress “Edit/String” button and scroll to the desired shot 

string. Depress “Enter” Button, to select string. Depress “Clear/ 

Reset” button “del” will display with an indicator above “String”. 

depressing “yes” button will delete current string. if you choose 

not to delete string depress the “no” button which will default 

back into the edit string mode and allow scrolling through the 

recorded shot data. 

Statistical Data 

depress “Stats” button and the highest velocity reading within 

string will be displayed. use “Scroll” button to scroll right to view 

the lowest velocity reading, average velocity, extreme spread and 

the standard deviation of all shots recorded within the current 

shot string. Depress “Enter” button to exit Stats Mode, or if the 

statistical data reveals an erroneous velocity the velocity reading 

may be discarded by simply depressing the “edit String” button 

and scrolling to select desired velocity and repeat the delete 

Velocity instructions from above. 

Delete All Data 

Depressing the “Clear/Reset” button once will display “del”, 

depressing the “Clear/Reset” button a second time will display 

“res” with an indicator above “String” (see Figure 12). Depressing 

the “yes” button will delete all shot velocity data stored in memory, 

and the unit will automatically shut down. if you choose not to 

delete all memory depress the “No” button to exit out of “Clear/ 

Reset” mode. 

Figure 12 - Reset Display to Delete ALL Data 

ADDITIONAL INFORMATION 

DISPLAY UNIT 

The display unit is what sets the AmmoMaster ® Chronograph apart 

from the competition. The functionality of the AmmoMaster ® display 

was designed with the shooter in mind. it allows the user to easily 

review statistical data and to review or edit recorded data in memory 

at any time during operation. The keypad was also designed with the 

appropriate commands necessary to allow the user to step through 

any operation with ease. Though data operations are simple to do, we 

strongly encourage the user to read through the appropriate sections 

in this manual. 

1. Depress On/Off button, “rcbs” will display. The unit will, if there is 

no previous recorded data, be ready to record shot #1 in string #1. 

The unit will display “1” with an indicator shown directly beneath the 

“String” header, then disappear and flash with an indicator displayed 

directly beneath “Ready” and “Shot” headers (see Figure 13). This 

menu informs the user that the unit is ready to record shot velocity 

#1 in string #1. 

• If unit has recorded velocities from a previous session, please 

read Previous Recorded Data section below. if you would like to 

remove all previously recorded shot velocities, refer to the Delete 

All Data function on the previous page. 


Figure 13 - “Ready” on “Shot” 1 

2. While recording shot velocities, the most recent velocity 

measurement can easily be deleted by pressing the “delete data” 

button. The word “del” will show on the display (see Figure 14). 

Depressing the “Yes” button will confirm the deletion of the last 

recorded velocity. depressing the “no” button will prevent deletion 

of velocity and resume recording shot velocities within the existing 

string. 

Figure 14 - Delete Current Velocity Data Point 

3. Once you have fired your tenth and final shot in a string, the display 

will flash between “FULL” and “1”, (see Figure 15). This means that 

string 1 is full with ten recorded shot velocities. 

• To start a new shot string, depress “Enter”. If all shot strings are 

full, refer to the Delete String and/or the Delete All Data section 

above to allow for recording more shot velocities 

• To view the High, Low, Average, Extreme Spread, and Standard 

Deviation of the current shot string velocities - depress the “Stats” 

button and refer to the Statistical Data section below. 

• If you choose to scroll through and verify shot velocities recorded 

- depress the “Edit String” button and use the “Scroll” buttons to 

scroll through the recorded shot velocities. 

Note: When 100 shots have been recorded, all memory allocations 

are full. Some or all of the data must be deleted in order to continue 

collecting velocity data. The chronograph will not overwrite subsequent 

data if you continue to shoot. 


Figure 15 - Full String of Data 

EDIT STRING FUNCTION 

1. The Edit String function is one of the most useful functions on the 

AmmoMaster ® Chronograph. By depressing the “edit String” button, 

the unit will default to the highest string number with recorded shot 

velocities. For example, if there are nine full shot strings and the 

“edit String” button is depressed, the display will show an indicator 

displayed directly under “String” and the display will show a “9”. 

2. At this point the user is allowed to scroll through shot strings and 

select the desired string to review. After determining which string to 

review, depressing the “enter” button will select the desired string. 

The unit will flash between the last shot velocity recorded in the 

string and its corresponding velocity. 

3. The user can scroll through and review shot velocities. An erroneous 

velocity reading is easily deleted by depressing the “delete data” 

button, followed by the “yes” button. This will shift all numbers 

down. For example, if there were 8 shot velocities recorded within 

a particular string and shot 4 velocity was deleted, shots 1-3 will 

remain unchanged. however, the old shot 5 will become the new 

shot 4, and the old shot 6 will become the new shot 5, etc. up to 

shot 7. The string can be filled by appending new shot velocities by 

simply depressing the “Add data” button or the “enter” button. The 

display will flash between string and shot, which means the unit is 

ready to record the next velocity reading and you can begin shooting. 

Or, by pressing “Enter” again, the unit will begin on shot 1 of the next 

blank string. 

PREVIOUSLY RECORDED DATA 

if there is stored shot velocity data, the unit will display “rcbs” and 

then automatically default to the highest level string that has no data. 

For example, if strings 1-9 have stored velocity data and string 10 has 

none, the unit display will flash “10” with an indicator on “String” and 

flash “1” with an indicator on “Shot”. This means the unit is ready to 

record shot 1 in string 10. 

Note: If there are strings that are not completely filled, i.e., having 

less than 10 shots per string, the unit will default to the highest level 

string containing data. if this string happens to be full the display will 

flash between “full” and the string number you are currently in. for 

example, if in string 10; the unit display will flash between “FULL” and 

“10”; meaning string 10 is full. 

it is possible to access and record shot velocities to strings with 

no previously recorded data by using the “edit String” function. for 

example, if string 4 has no data and all of the remaining strings are 

full, the unit will default to string 10 and show that string 10 is full. 

(The only way for this to happen is if the user physically deleted 

all the recorded shot velocities within string 4.) You can depress 

“Edit String” and use “Scroll” to locate string 4. Depressing “Enter” 

will select string 4 and the unit display will flash between shot “1” 

and velocity “- - - -”, meaning you are in string 4 but there are no

ecorded velocities (see Figure 16). Depressing “Enter” again, or 

the “Add Data” button, the display will flash between “String” 4 and 

“Ready” on “Shot” 1. Now the unit is ready to record shot 1 in string 4. 

Figure 16 - Display for No Data in String 

SKYSCREEENS 

your AmmoMaster ® Skyscreens operate using standard photocell 

technology. The photocell is constantly gathering incoming light. When 

an instantaneous change in light is detected, the photocell saves the 

time at which this occurs. For example, when a projectile is fired over the 

Start Skyscreen of the Chronograph, the shadow cast by the projectile 

triggers the photocell at a moment in time. The instant the projectile 

passes over the Stop Skyscreen, the shadow cast by the projectile 

triggers the photocell at another moment in time, thus generating a 

start and stop time. Since the Skyscreens are manufactured with a 

known distance between them, the projectile velocity can be calculated 

using the equation Velocity = Distance ÷ Time. 

DIFFUSERS 

The diffusers for your AmmoMaster ® Chronograph play a very important 

role in recording velocity readings. The diffusers are used to help 

filter out any unnecessary incoming light. This aids in the photocell’s 

ability to detect a slight change in light as a projectile passes over 

the Skyscreen. if the diffusers are not used on a clear, sunny day, the 

photocell may be saturated by all the incoming light and may not detect 

the shadow cast by the projectile. imagine trying to spot an object flying 

through the air as it passes directly in front of the sun; this is similar 

to using the chronograph without any diffusers on a clear sunny day. 

Again, imagine trying to spot the same object flying through the air as 

it passes directly in front of the sun but this time, there is an overcast 

condition. The object is much easier to see. This analogy is similar to 

using diffusers on your Chronograph. 

LIGHTING CONDITIONS 

now that you have a basic understanding of what makes your 

chronograph function, you know that the lighting conditions are 

very important. A Skyscreen’s accuracy and sensitivity to changes in 

illumination is based on the ambient lighting conditions. While they 

work most of the time, chronographs do have limitations which will 

cause errors. Too much light, as well as not enough light, will inhibit the 

chronograph operation. 

in low light situations, i.e., early morning, late evening, overcast or 

cloudy conditions, the chronograph may produce inconsistent velocity 

measurements or may not record velocity readings at all. Try removing 

the diffusers to allow more light to reach the photocell. 

problems can also arise on clear, sunny days when shooting over snow, 

water, or light colored sand/gravel, etc. Reflected light off the ground 

can illuminate the bottom of the bullet and cancel the shadow cast onto 

the skyscreen causing erroneous velocity readings. When this happens, 

try covering the ground around the chronograph with a blanket or nonreflective 

tarp. This should minimize the reflected ground light and 

alleviate the problem. Another technique is to color the bullet with a 

black marker, especially if the bullets have a shiny appearance. 

in locations with direct overhead sunlight, the Skyscreen may become 

saturated by the incoming light, even when the diffusers are installed. 

Excessive light can cause a blind condition and the photocell may not 

“see” the bullet pass over. This is because the small bullet’s shadow 

is not providing sufficient contrast. To reduce the amount of input light, 

try covering the diffuser’s top surface with any material that will absorb 

or reflect the light (aluminum foil, cloth material, cardboard, etc.) Don’t 

use anything heavy enough to disrupt the units balance or damage the 

diffuser or Side Supports. if all else fails, it might be best to come back 

and shoot another day or wait until later in the day when the light has 

subsided. 

INDOOR SHOOTING 

To use indoors, you must provide the chronograph with an artificial light 

source. Install a standard incandescent light bulb centered 24 inches 

above each diffuser to provide a uniform illumination. We recommend 

using a 60 – 100 W bulb and an aluminum reflector dish for each 

light fixture, if possible. These products are readily available at most 

hardware stores. 

Other lighting configurations may provide acceptable results (different 

installation height, no reflector dish, etc.), but be slightly less accurate. 

fluorescent light sources will not work reliably because they do not 

provide a continuous light source. 

SHOTSHELL VELOCITY 

it is highly recommended that you determine your shot’s pattern 

size before starting. Only use your Diffusers and Side Supports if your 

gun’s shot pattern is small enough to pass through the chronograph’s 

shooting area without causing damage. fAiluRe To do So MAy CAuSe 

SeRiouS dAMAge To The SkySCReen oR oTheR CoMponenTS And 

poTenTiAlly CAuSe SeRiouS inJuRy To The ShooTeR. 

To prevent damage to your Chronograph, we recommend removing 

the diffusers and Side Supports when measuring shotshell velocity. 

Position weapon 10 feet away from chronograph (see Figure 9) and 

continue using as you would for centerfire rifle ammo. Certain ambient 

and environmental conditions can result in erratic measurements when 

the diffusers are not used. See “lighting Conditions” section for more 

information. 

To measure your shot pattern, place a paper target approximately 15 

feet from the muzzle of your firing position. Shoot into the target to 

measure the diameter of the shot pattern. Then, determine a desired 

aiming point to ensure you are shooting approximately 4-6 inches 

above the chronograph Skyscreens. once this has been done place 

your chronograph so the back of the unit is against the target. Verify 

the shot pattern is the correct height above the skyscreens. Move the 

target a few feet further away (ie., down range) from the chronograph 

and begin recording velocities. 

ARROW VELOCITY 

for better measurement accuracy, make sure you are far enough away from 

the chronograph so that the arrow separates completely from the bow string 

before the tip reaches the “Start” skyscreen. Blunt arrow tips work best. 

STATISTICAL DATA 

Statistical data only applies to the recorded data within a selected shot 

string, not multiple strings. Therefore, the largest sample size for any 

statistical data measurement will be a sample size of ten. 

High Velocity 

displays highest recorded velocity within selected shot string. 

Low Velocity 

displays lowest recorded velocity within selected shot string. 


Average Velocity 

displays the statistical average of the recorded velocities within an 

existing shot string. 

Extreme Spread 

displays the difference between the highest and lowest velocity readings. 

Standard Deviation 

Standard deviation (S.D.) of a string is a measure of uniformity of the 

data. it essentially tells you how much scatter is present in the data set 

relative to the average velocity. The smaller the number is, the better 

your data’s uniformity. A standard deviation of zero would mean that 

every velocity was identical. An S.D. value approximates that 68% of 

data will fall within ± 1(S.D.) of the Avg. velocity, 95% of all recorded 

velocities will fall within ± 2(S.D.) of the Avg. velocity, and 99% of all 

recorded velocities will fall within ± 3(S.D.) of the Avg. velocity. 

Example: Let’s say we have a full shot string of 10 shots. From pushing 

the Stats button we find the following information: 

High Velocity: 3100 f/s 

Low Velocity: 3000 f/s 

Avg. Velocity: 3050 f/s 

Extreme Spread: 100 f/s 

Standard Deviation: 10 f/s 

With a standard deviation of 10 f/s, the worst anyone can expect is that 

99% of the shot velocities are within ± 3(S.D.) of the Avg. Velocity or 

3050 ± 30 f/s. , which equates to 3080 f/s to 3020 f/s, respectively. 

BATTERY INFO 

The AmmoMaster ® Chronograph operates using a 9V battery. 

We recommend using high quality batteries for optimal performance. 

A good alkaline battery life under nominal lighting conditions should 

last approximately 5 – 6 hours. 

REPLACEMENT PARTS 

Should you accidentally shoot your chronograph (and most people who use 

them long enough eventually will), just call us to order replacement parts. 

The following replacement parts are available for purchase from RCBS: 

Skyscreens # 81193 

Diffusers # 81192 

Side Supports (2 pack) # 81191 


LIMITED WARRANTY 

your AmmoMaster ® Chronograph is warranted to be free from defects 

in material or workmanship for one year from the date of purchase. 

This warranty is extended only to the original consumer purchaser. 

All RCBS products are intended for non-commercial use by hobbyists. 

Any other use of these products will void the warranty. Should you 

believe that your AmmoMaster Chronograph is defective in material 

or workmanship, you must return the AmmoMaster Chronograph to 

Ammunition Accessories Inc. through its Oroville operation (hereinafter 

“Oroville Operations”) postage paid, for evaluation. If defective, the 

product will be repaired or replaced at oroville operations’ option, at 

no charge. 

Send a dated proof of purchase to oroville operations for return shipping 

and handling, along with the defective product or parts to: 

Ammunition Accessories inc., oroville operations 

605 Oro Dam Blvd East 

Oroville, California 95965 

Warranty services cannot be provided without meeting the above 

requirements. 

To enSuRe ACCuRACy of youR WARRAnTy infoRMATion, Send 

youR WARRAnTy CARd To: 

Ammunition Accessories inc., oroville operations 

605 Oro Dam Blvd East 

Oroville, California 95965 

ThiS one yeAR liMiTed WARRAnTy doeS noT CoVeR defeCTS oR dAMAge 

ReSulTing fRoM: CAReleSSneSS, MiSuSe, CoMMeRCiAl uSe, ABuSe, iMpRopeR 

inSTAllATion, ModifiCATion, oR noRMAl WeAR And TeAR. The iMplied WARRAnTieS 

of MeRChAnTABiliTy And fiTneSS foR A pARTiCulAR puRpoSe ARe liMiTed To The 

duRATion of ThiS one yeAR liMiTed WARRAnTy. oRoVille opeRATionS iS noT liABle 

foR dAMAgeS in eXCeSS of The puRChASe pRiCe of The pRoduCT And undeR no 

CiRCuMSTAnCeS ShAll oRoVille opeRA TionS Be liABle foR ConSeQuenTiAl oR 

inCidenTAl dAMAgeS. hoWeVeR, SoMe STATeS do noT AlloW liMi TATionS on 

inCidenTAl, oR ConSeQuenTiAl dAMAgeS, So The ABoVe liMiTATion oR eXCluSion 

MAy noT Apply To you. 

dAMAge To The uniT CAuSed By BulleT iMpACT iS noT CoVeRed undeR 

WARRAnTy. 

The above warranty provides the sole and exclusive warranty available to the customer 

in the event of a defect in material or workmanship in the AmmoMaster ® Chronograph. 

This warranty gives you specific legal rights, and you may also have other rights which 

vary from State to State. 

RC119 9060

AmmoMaster® Chronograph Operating Instructions ... - RCBS

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